Conventional footwear manufacture has continued to rely on hand-stitching and adhesives to assemble footwear components into a finalized product. For example, individual components comprising the lower (e.g. outsoles) and uppers (used herein to refer to midsoles, side walls, and other upper components), may be hand-stitched and/or adhered together to form a finished product. The reliance on manual labor and the assembly from multiple components results in variations in the footwear, including variations in sizing and quality.
To accommodate the variety of methods and tools for making various shoe styles, a single footwear manufacturer may maintain many types of skilled labor, stocks of raw materials and production machinery that are used to produce a variety of footwear elements. The variety in manufacture complicates shoe construction across an entire product line and may cause further difficulty in achieving uniform sizing.
Furthermore, different methods of shoe construction require specialization in skills. Strobel lasted shoes are common among casual, athletic and work footwear, among others. A strobel sock spans the interior or a portion of the bottom of an article of footwear and may be hand stitched to the upper. Strobel lasting may provide increased stability, flexibility or durability in addition to weight savings to an article of footwear. Because of the three dimensional structure of the footwear where the strobel meets a shoe upper, and the often narrow spacing for the stitch, this type of assembly may utilize extensive, and complicated hand labor. Additionally, strobel construction may further make extensive use of adhesives to affix the strobel sock to the shoe upper and/or midsole.
As mentioned above, to assemble the many individual components, footwear construction approaches commonly use solvent-based adhesives to bond various components together. For example, solvent-based adhesives, including organic solvents, may be used in the footbed, the outsole, the midsole, the insole, etc. Different materials may be coupled together using adhesives such that the footwear is held together primarily by adhesives.
When used in the construction process, solvent-based adhesives may emit volatile organic compounds (VOCs), which can produce indoor and/or outdoor air pollution, and thus, degrade the quality of the environment. In addition to emissions generated during the application and/or curing processes, excess adhesive in the manufacturing process may also be considered environmental waste, also potentially impacting the quality of the environment. In fact, various regulations exist with regard to use, handling, and disposal of solvent-based adhesives.
In addition to the use of adhesives, traditional injection molding is typically used to form components or portions of components of footwear. Many outsoles, midsoles and even uppers are produced by injection of a hardenable thermoplastic material, typically polyurethane, into preformed molds. Conventional methods of injection molding inject the material into a mold, which seals around the material as it dries. Molds that are worn, poorly constructed or overfilled may not form an effective seal resulting in material spilling beyond the mold, known as flashing. Because the moldable material is injected directly into the mold, traditional injection molding requires extensive cleaning upon removal of hardened products. Additionally, every variation to a traditional injection molded product, such as alteration in sizing, design, pattern, or structure requires a new mold resulting in a costly process.
Injection molding of polyurethane or a similar thermoplastic material in the presence of a textile is used in a variety of contexts in constructing footwear. For example, injection molding of textiles has been used to bond fabric shoe uppers to an injection molded insole, to create foam-filled shoe uppers, fabric-bonded boot liners and the like. The injection molding of textiles also uses a mold manufacture style. In some embodiments, an aluminum casting may be closed and sealed around the moldable material. In the case of fabric-bonded injection molded footwear components, the mold may be lined with a textile. Foam may be injected into the fabric lined mold so that, as the foam dries, the hardenable material adopts the shape of the mold and becomes bonded to the fabric. Like conventional injection molding in the absence of a fabric layer, cleanup of molds after hardening is extensive. Additional processing methods are typically required including trimming of excess injected or fabric material, and stitching, adhering or otherwise attaching additional design elements.
The Inventors herein have recognized the above several drawbacks of traditional methods of shoe manufacture. As discussed above, the heavy reliance on solvent-based adhesives can negatively impact the quality of the environment during construction. Additionally the reliance on construction by hand and multiple methods of manufacture for varied product types complicates the manufacture process and makes uniformity in sizing difficult. Traditional construction of footwear articles comprising a strobel sock makes use of extensive and complicated hand labor. Furthermore, traditional methods of injection molding and of fabric-bonded injection molding require extensive set up and cleaning of molds during manufacture. The reliance on molds makes for a significant investment in different molds across a product line to produce elements in varied sizes and styles. Moreover, conventional methods of fabric-bonded injection molding produce components of footwear that necessitate additional structures and assembly for development into completed footwear.
Recognizing these drawbacks, the Inventors describe herein a port-injection footwear in which use of a closed mold is unnecessary and in particular strobel lasted, port-injection footwear. Obviation of the traditional mold is achieved by direct injection of foam, such as polyurethane, into a bag, such as a footwear-structure bag. This bag forms a substantially sealed cavity between a foot surface and the exterior to form an integrated footwear component, such as a portion of an upper. The bag forms an integrated footwear component (e.g. one or more of midsole, insole, sidewall and upper), protected by the attached outsole. A stretchable strobel sock may further be integrated into the footwear structure bag. However, in other examples, the strobel sock may be integrated into the outsole. Integration of multiple elements of footwear to form an integrated footwear component simplifies manufacture and produces a product which may be more durable and/or stable. Further, the reduction in adhesives enables footwear incorporating the direct injection method to reduce negative impacts on the quality of the environment. Reduction in adhesive use further reduces labor in shoe construction and may create a more flexible shoe structure when desired.
The present application discloses port-injection footwear made with a strobel sock. The strobel sock may provide weight savings and added flexibility to an article of footwear. Utilizing a stretchable material a strobel sock may be incorporated into a footwear-structure bag that is then injected with foam or other material in the presence of an elongated last that is extended in the base of the footform compared to a conventional last. Upon removing the elongated last the strobel sock shrinks back to its original size and forms a footbed of an article of port-injection footwear. Additional steps and extensive hand stitching to finish the footwear may be avoided in this way.
Port-injection footwear of the present disclosure may be adapted to a variety of types of footwear. The substantially sealed bag that retains the injected foam may be attached to many types of outsoles by a variety of attachment methods. Also, the shoe sidewalls and upper may adopt different shapes and utilities, such as that of a sandal, boot, sneaker or other type of footwear.
Thus, in summary, the inventors herein disclose port-injection footwear having a footwear-structure bag with an integrated strobel sock encompassing a foam core. The bag may be attached to a separately formed outsole. In one embodiment, the footwear of the present disclosure may have an integrated upper formed at least partially by a footwear-structure bag inflated by an injectable polymer and an insole comprising a strobel sock. Furthermore, the footwear of the present disclosure may be formed while the bag is expanded during injection around an elongated last or foot-shaped form. With a uniform, elongated last, regularity of sizing may be achieved as the strobel sock shrinks to original size when the elongated last is removed. The method of the present disclosure allows for widely varied product design and finish detailing such as pattern and shape molding, which may be achieved using modular shaping tools that can be used across footwear styles and sizes and may not fully enclose nor seal onto the direct injected foam material.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.